Now the code is completely in line with the documentation, but still nothing works.

<div class="twitch-embed-div">
   <div id="twitch-embed">
      <iframe src="https://embed.twitch.tv/?channel=xop0&height=300&migration=true&muted=true&parent=freetp.org&theme=dark&width=525" allowfullscreen="" 
      scrolling="no" allow="autoplay; fullscreen" title="Twitch" width="525" height="300">
      </iframe>
   </div>
      <script type="text/javascript">
         new Twitch.Embed( 'twitch-embed', {
            width   : 525,
            height   : 300,
            channel   : 'xop0',
            muted   : true,
            theme   : 'dark',
            parent   : ['freetp.org']
         } );
      </script>
  </div>

The issue is still not resolved, but you have already hidden this topic.
At the same time, twitch support also does not give any information and directs it here. Vicious circle.